The present invention relates to an analog-to-digital (A/D) converter, an A/D converter control method, and an A/D converter connection method. More particularly, the present invention is concerned with an A/D converter making it possible to reduce the power consumption of an output interface, and a control method and a connection method for the A/D converter.
In the past, a low-voltage differential signaling (LVDS) technology has been known as a technology for transmitting a low-voltage differential signal over a signal line pair while reducing power consumption or electromagnetic interference (EMI) (refer to, for example, Non-patent Document 1).
[Non-Patent Document 1] LVDS Owner's Manual & Design Guide (spring in 1997, National Semiconductor)
In recent years, an attempt has been made to employ a low-voltage differential signaling (LVDS) technology in transmitting an output of an A/D converter incorporated in a diagnostic ultrasound system.
In the LVDS technology, an output current shall be approximately 3.5 mA, a resistance of a terminal resistor shall be 100Ω, and a voltage at both terminals of the terminal resistor shall be 350 mV. Assuming that a supply voltage is 2 V and a margin offered by an A/D converter is about 30%, a power of approximately 10 mW is always consumed for each signal (a current flows all the time because it carries a differential signal).
On the other hand, the power consumption of an A/D converter itself is being reduced and has decreased to approximately 20 mW these several years.
However, when the power consumption of the A/D converter itself has decreased to approximately 20 mW, the consumption of the power of approximately 10 mW by an output interface cannot be ignored.